Conventionally, a tractor corresponding to one example of the working vehicle has been provided with a travel machine body to which an engine and a transmission case are mounted, and a ground working machine such as a rotary tiller or the like which is installed to a rear portion of the travel machine body via a link mechanism so as to be movable up and down. A part of a rotary power transmitted from the engine to the transmission case is transmitted to the ground working machine via a PTO shaft which is provided in a protruding manner in the transmission case, and the ground working machine executes a predetermined work, for example, a plowing-up and tilling work (refer, for example, to patent document 1).
In this kind of tractor, an engine controller actuates a fuel injection device with electronic governor on the basis of an output characteristic map, thereby achieving a target rotating speed corresponding to an amount of operation of a throttle lever or a shift pedal, and regulates a fuel injection amount in such a manner as to correspond to a load, thereby controlling an engine output (a rotating speed and an output torque). For example, it has been well known that a reverse droop control giving tenacity to the engine output is executed in a low speed range of the rotating speed.